Speaking at the opening plenary session of the summit, Mr Putin suggested the topic be on the agenda over dinner.

"Some participants have asked me to give the time and possibility to discuss other... very acute topics of international politics, in particular the situation around Syria," he said.

"I suggest we do this during dinner so that we... in the first part can discuss the (economic) problems we had gathered here for and are key for the G20."

EU urges diplomatic efforts on Syria and 'no military solution'

Ahead of the summit Europe's top officials warned against a military response in Syria, aligning themselves more closely with Mr Putin than Mr Obama in how best to respond to the use of chemical weapons in Syria.

While describing the August 21 attack near Damascus, in which an estimated 1,400 people died, as "abhorrent" and a crime against humanity, European Council president Herman Van Rompuy said a military strike would not help resolve the crisis.

"There is no military solution to the Syrian conflict," Mr Van Rompuy told reporters.

"Only a political solution can end the terrible bloodshed, grave violations of human rights and the far-reaching destruction of Syria.

"While respecting the recent calls for action, we underscore at the same time the need to move forward with addressing the Syrian crisis through the UN process."

His position, supported by European Commission president Jose Manuel Barroso, would appear to set the European Union at odds with the US, since Mr Obama has said he is prepared to launch military strikes once he has approval from Congress, where votes are expected next week.

It also suggests internal divisions within the EU. France, which with Britain is the most influential of the EU's 28 member states on foreign policy, has said it will support any military action taken by Washington.

British prime minister David Cameron was also keen to support military intervention, but he lost a parliamentary vote on the issue last week and Britain will not take part.